Technical Abstract:
In order to understand which viral genes contribute to the high virulence of A/Dk/Vietnam/201/05 H5N1 highly pathogenic avian influenza (HPAI) virus in ducks, we used reverse genetics to generate single-gene reassortant viruses with genes from A/Ck/Indonesia/7/03, a virus that produces mild disease in ducks. Ducks were intranasaly inoculated with the reassortant viruses. Exchange of the HA and NA genes resulted in increased mortality, decreased mean death times and increased distribution of viral antigen staining in the tissues. This study permitted the identification of the genes involved in increased pathogenicity of H5N1 HPAI viruses in ducks.